Solventless laminating adhesive for flexible packaging laminations and laminated structures made with the adhesive

ABSTRACT

Two-component solventless adhesive compositions for lamination applications and laminated structures, including flexible laminated packaging, comprising at least two substrates, including structures comprising reverse printed ink films and/or metallized films. The adhesive comprises a prepolymer having one or more oligomers with a relatively high molecular weight.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application No.61/359,646, filed Jun. 29, 2010. U.S. Patent Application No. 61/359,646is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention pertains to two-component solventless adhesivecompositions for lamination applications and structures, such aslaminations and flexible laminated packaging, including those comprisingmetal or ink decals, comprising and/or made with the two-componentsolventless adhesive composition. The two-component solventless adhesivecomposition is softer than conventional two-component solventlessadhesive compositions but retains the beneficial properties ofconventional adhesives. The adhesive composition described hereincomprises relatively high molecular weight oligomers and has anelongation.

The Related Art

Flexible packaging structures were traditionally made with solvent-bornelaminating adhesives. Over the past 20-30 years, new water-borne andtwo-component solventless adhesives have been developed andcommercialized to replace solvent-borne adhesives due to the benefit oflower costs and a desire in the industry for more environmentallyfriendly adhesives. However, some applications today remain usingsolvent-borne adhesive technology because of the specific performance ofthat technology and the properties of the substrates being bonded. Thus,two-component solventless laminating adhesives are not useful for allstructures and applications.

Problematic structures for two-component solventless adhesives include(1) reverse printed film (i.e., polyethylene terephthalate (“PET”)) tometallized film (i.e., PET) and (2) reverse printed PET film withwater-base inks to secondary films. Presently these structures aretypically made with either solvent-borne or water-borne laminatingadhesives. Metallized film is generally a plastic film sheet havingattached to the film a layer of metal, generally a thin metal layer.Metallized films are used in flexible laminated packaging materialswhere it is desired to reflect light from the contents of the packagingor for visual appearance of consumer packaging.

Typical structures of reverse printed PET laminated to the metal side ofmetallized PET with typical two-component solventless laminatingadhesive results in low bonds with up to 100% metal failure from themetallized PET. Such failure result typically does not happen when usingsolvent-borne or water-borne laminating adhesives. When two-componentsolventless adhesive is applied with reverse printed PET with water-baseinks, the water-base ink decals off of the PET at lower bond values.

Conventional two-component solventless adhesives comprise relativelylower molecular weight monomers and relatively lower molecular weightoligomers that typically act as reactive diluents. These low molecularweight reactive materials generally provide favorable characteristicsand properties for many, but not all, laminating applications. Withoutwishing to be bound by any theory, the inventor believes that inspecific applications, such as those discussed above involving reverseprinted film to metallized film and reverse printed film, includingreverse printed PET film, with water-base inks to secondary films, therelatively lower molecular weight monomers and relatively lowermolecular weight oligomers contribute to the negative affects ofdecalling metal (demetallization) or ink from the film.

All parts and percentages set forth herein are on a weight-by-weightbasis unless specified otherwise. The molecular weight referred toherein is the number average molecular weight (Mn) in grams/mole(“g/mole”).

SUMMARY OF THE INVENTION

The two-component solventless adhesive described herein improves bondstrength in many applications, including in structures comprising eitherthe metal or ink decals. The two-component solventless adhesive issofter than conventional two-component solventless adhesives butmaintains many of the same benefits as conventional two-componentsolventless adhesives such as low enough viscosity to apply at 100%solids, good adhesion, chemical resistance, and the like.

The two-component solventless adhesive comprises high molecular weightoligomers, i.e. oligomers having higher molecular weight than oligomersused in conventional two-component solventless adhesives. Thetwo-component solventless adhesive is suited for any laminationapplication but is particularly suited for applications whereconventional solventless adhesives provide poorer performance, such asfor (1) reverse printed film (i.e., PET) to metallized film (i.e., PET)and (2) reverse printed film, including reverse printed PET film, withwater-base inks to secondary films.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a side, cross-sectional view of a laminated flexiblepackaging material in accordance with the invention.

FIG. 2 illustrates a side, cross-sectional view of a laminated flexiblepackaging material in accordance with the invention.

FIG. 3 illustrates a side, cross-sectional view of a laminated flexiblepackaging material in accordance with the invention.

FIG. 4 is a graph showing bond value in relation to curing time in daysfor a reverse printed 48 gauge PET and metallic PET film laminatedstructure.

FIG. 5 is graph showing bond strength for various laminated structurescomprising water-base ink printed films made with various conventionaladhesives.

FIG. 6 is a graph showing bond strength for various laminated structurescomprising water-base ink printed films made with control adhesiveformulations and adhesive formulations in accordance with the invention.

FIG. 7 is a graph showing bond strength for various laminated structurescomprising metallized films made with control adhesive formulations andadhesive formulations in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Two-component solventless adhesives are supplied as two separatecomponents and mixed prior to application followed by curing. The twocomponents are called the prepolymer and the curative. The two-componentsolventless adhesive has no solvent and/or is applied without solvent,such as organic solvent or water.

The two-component solventless adhesive comprises oligomers havingrelatively high molecular weight, such as oligomers having molecularweight in excess of about 1,000 g/mole, typically oligomers havingmolecular weight of at least about 3,000 g/mole such as about 3,500g/mole or more, for example oligomers having a molecular weight of aboutat least 8,000 g/mole and also those having molecular weight in excessof about 10,000 g/mole. Included are oligomers having molecular weightin the range of about 3,500 g/mole to about 20,000 g/mole.

The two-component solventless adhesive composition may comprise acombination of relatively high molecular weight oligomers, havingdifferent molecular weights. Thus, the two-component solventlessadhesive may have a first oligomer and, in embodiments where acombination of oligomers are present, a second oligomer. For example,the combination of oligomers having a molecular weight of about 2,000g/mole to about 5,000 g/mole, preferably about 3,000 g/mole to about5,000 g/mole including about 3,500 g/mole to about 5,000 g/mole, andanother having a molecular weight of about 5,000 g/mole to about 10,000g/mole or more, such as about 5,500 g/mole to about 10,000 g/mole.

The two-component solventless adhesive typically has 100% solidscontent, although in embodiments the adhesive may have less than 100%solids content. The molecular weight of the oligomer must be such that,when combined with other ingredients of the adhesive, the viscosity isnot too high for application without any or a significant amount ofsolvent.

Oligomers useful in the invention include all types of polyols, forexample polypropylene oxide having relatively high molecular weight.Polyether polyols such as polyoxypropylene glycol, polyoxyethyleneglycol and copolymers of ethylene and propylene oxide may also be used.Also, polyesterpolyols such as those compositions obtained from diacidsor higher such as, adipic acid, and various alkane diols are useful.Examples of alkane diols include 1,3-propanediol, 1,4-butanediol,1,5-pentanediol and 1,6-hexanediol. Other useful polyols are obtained bycopolymerizing at least one compound of ethylene oxide, propylene oxide,butylene oxide, tetrahydrofuran, and the like with at least one compoundhaving at least two active hydrogen atoms on average in one moleculesuch as polyhydric alcohols which include ethylene glycol, propyleneglycol, dipropylene glycol, glycerol and the like. Other suitablepolyhydric compounds include sucrose, ethylenediamine, propylenediamine,triethanolamine, 1,2-propanedithiol, and the like.

Typically, the oligomers are incorporated into the prepolymer; however,the oligomers can be incorporated into the curative or in both thecurative and prepolymer. Preferably, the oligomers have relatively lowviscosity.

The oligomers are incorporated in relatively high amounts and can beincorporated as all or part of the total amount of oligomer in atwo-component solventless adhesive formulation. For example, when therelatively higher molecular weight oligomers are incorporated into theprepolymer, the amount of such oligomers may be at least about 20% byweight of the prepolymer, such as at least about 40% by weight of theprepolymer and may be as high as at least about 60% by weight of theprepolymer, including in the ranges of about 20% by weight to about 80%by weight, such as about 20% by weight to about 60% by weight, such asabout 20% by weight to about 40% by weight, all by weight of theprepolymer.

The prepolymer may comprise other components typically found in theprepolymer part of two-component solventless adhesives, such asisocyanates. Isocyanates useful in the prepolymer of the inventioninclude hexamethylene diisocyanate, toluene diisocyanate (TDI),diphenylmethane diisocyanate (MDI) (which is available commercially asMONDUR® MR from Bayer Material Science, Pittsburgh, Pa., USA),allophonate-modified diphenylmethane diisocyanate (allophonate modifiedMDI which is commercially available as MONDUR MA from Bayer MaterialScience), m- and p-phenylene diisocyanates, bitolylene diisocyanate,cyclohexane diisocyanate (CHDI), bis-(isocyanatomethyl)cyclohexane(H₆XDI), dicyclohexylmethane diisocyanate (H₁₂MDI), dimer aciddiisocyanate (DDI), trimethyl hexamethylene diisocyanate, lysinediisocyanate and its methyl ester, isophorone diisocyanate, methylcyclohexane diisocyanate, 1,5-napthalene diisocyanate, xylylene andxylene diisocyanate and methyl derivatives thereof, polymethylenepolyphenyl isocyanates, chlorophenylene-2,4-diisocyanate, polyphenylenediisocyanates available commercially as, for example, MONDUR MR orMONDUR MRS (both available from Bayer Material Science), isophoronediisocyanate (IPDI), hydrogenated methylene diphenyl isocyanate (HMDI),tetramethyl xylene diisocyanate (TMXDI), hexamethylene diisocyanate(HDI), or oligomer materials of these materials such as a trimer ofIPDI, HDI or a biuret of HDI, and the like and combinations thereof. Thepreferred isocyanate comprises MDI, such as MONDUR MA from BayerMaterial Science, which is an allophonate modified MDI. Typically, whenthe prepolymer part includes both polyol and isocyanate, the isocyanatecontent of the prepolymer is about 5% to about 25%, preferably about 6%to about 17%.

The prepolymer part of the two-part solventless adhesive compositiontypically comprises the relatively high molecular weight oligomers andisocyanate. For example, in an embodiment the prepolymer comprisesisocyanate and oligomers having molecular weight in excess of about1,000 g/mole, typically oligomers having molecular weight of at leastabout 3,000 g/mole such as about 3,500 g/mole or more, for exampleoligomers having a molecular weight of about at least 8,000 g/mole andalso those having a molecular weight in excess of about 10,000 g/mole.Included are oligomers having a molecular weight in the range of about3,500 g/mole to about 20,000 g/mole. In a further embodiment, theprepolymer comprises a combination of relatively high molecular weightoligomers, having different molecular weights, for example a compositionhaving a molecular weight of about 2,000 g/mole to about 5,000 g/mole,preferably from about 3,000 g/mole to about 5,000 g/mole including about3,500 g/mole to about 5,000 g/mole and another having a molecular weightof about 5,000 g/mole to about 10,000 g/mole or more, such as about5,500 g/mole to about 10,000 g/mole. The prepolymer may consistessentially of or consist of these components and combinations.

In addition, the relatively high molecular weight oligomers can be usedin epoxy/amine solventless two-component adhesives.

The curative part of the two-component solventless adhesive may be anycurative typically used in two-part adhesives and is typically anisocyanate reactive curative. The curative part comprises an isocyanatereactive component, such as a component selected from the groupconsisting of polyhydroxyls, polythiols, polyamines, and the like, andcombinations thereof. The curative part may also comprise isocyanatesand/or oligomers, including those mentioned above with respect to theprepolymer. PURELAM® laminating adhesives available from Ashland Inc.,Dublin, Ohio, USA, like PURELAM 6050, may comprise the isocyanatereactive curative.

In addition to the above, other components may be included in thetwo-component solventless adhesive, in the prepolymer, the curative orboth the prepolymer and curative. These components includepolymerization control agents, inhibitors, antioxidants, wetting agents,adhesion promoters, fillers and the like. Polymerization control agentsinclude dibutyl tindilaurate and trimethyl amine. Fillers include finelydivided silicon dioxide, bentonites or calcium carbonate.

The prepolymer is generally made by reacting an excess amount ofisocyanate with an isocyanate reactive material, such as a polyetherpolyol, which results in the oligomers described herein and excessisocyanate. Other components of the prepolymer may be added prior to orafter the reaction. The curative may be made by reacting a diacid (orhigher order acid) with a glycol or a commercially available isocyanatereactive product may be used for the curative in the two-componentsolventless adhesive.

The two-component solventless adhesive is applied with any type ofsubstrates to create a laminated structure, and laminated structuresmade with or comprising the two-component solventless adhesive arewithin the scope of the invention, such as flexible laminated packagingmaterials. The adhesive is compatible with any substrates.

Metallized films are useful with the two-component solventless adhesive.The metallized films comprise a plastic sheet and a layer of metalgenerally deposited on the plastic sheet. The metallized film is usuallyformed prior to the process for making the laminated structuresdescribed herein. The plastic material of the metallized film may beselected from the group consisting of PET, biaxially orientedpolypropylene (“BOPP”), polylactic acid and polyethylene. The metallayer may be aluminum. Commercially available metallized films that maybe used in the invention include 48 gauge metallized polyester film(BARRIER-MET® Polyester) from VACUMET®, Austell, Ga., U.S.A. andmetallized oriented polypropylene (“OPP”) films (METTALYTE™ OPP) fromExxonMobil Chemicals, Houston, Tex., U.S.A., such as 70 gauge metallicOPP from ExxonMobil.

The two-component solventless adhesive inhibits, and in cases prevents,decaling (or demetallizing) of the metal layer from the plastic sheet ofthe metallized film in laminated structures wherein the metallized filmis laminated to one or more other substrates with the two-componentsolventless adhesive. Also, the two-component solventless adhesiveinhibits, and in cases prevents, decaling of water-base ink fromsubstrates in laminated structures wherein at least one substratecomprising water-base ink is laminated to one or more other substrates,including metallized substrates, with the two-component solventlessadhesive. Decaling or demetallizing can occur when the laminatedstructure is torn, in that the metal layer will be removed from theplastic sheet and remain attached to the other substrate in thelaminated structure or the water-base ink will remove from the printedsubstrate. This is undesirable, particularly with respect to flexiblelaminated packaging materials for consumer products.

The laminated flexible packaging materials may be formed by conventionalmeans understood to those skilled in the art. The laminated flexiblepackaging materials described herein can be produced using conventionaltechniques and replacing conventional laminating adhesives with thetwo-part solventless adhesive described herein. Generally, the processfor making the laminated structures comprises the steps of providing atleast two substrates, each having an upper surface and a lower surface,providing the two-component solventless adhesive described herein,applying the adhesive to a surface of at least one of the substrates andbonding the substrates together. Preferably, at least one of the twosubstrates is either printed with a water-base ink or comprises ametallized film substrate, and processes wherein one of the substratescomprises a water-base ink and the other comprises a metallized filmsubstrate are within the scope of the invention. Typical methods ofapplying adhesive include use of web coating methods such as rollcoating, gravure, offset gravure, and the like. The adhesive may beapplied and cured in-line with the printing or off-line in a separatelaminating step as desired.

When the prepolymer and curative are mixed, the adhesive begins to cureand continues to cure over a period of time until the adhesive cures.During curing, the oligomers in the prepolymer and the isocyanatereactive component of the curative react. The laminated structuresdescribed herein comprise a cured adhesive layer, which adhesive in theuncured state is the two-component solventless adhesive describedherein.

The laminated structures, such as the flexible laminated packaging,comprise at least two substrates, such as layers of flexible material,bonded together having at least one layer of the adhesive, a curedadhesive layer which is a cured form of the solventless two-partadhesive, between each substrate thereby forming a laminatedconstruction. Laminated structures, such as flexible laminated packagingmaterials, are illustrated in FIGS. 1-3. As shown in FIGS. 1-3, thestructures, i.e. laminated flexible packaging material, 1, 2 and 3comprise at least one second substrate, such as a second layer offlexible material, 4 laminated to a first substrate, such as a firstlayer of flexible material, 6 by the solventless two-part laminatingadhesive described herein 5, where layer 6 is the layer that will be onthe inside of the finished construction, i.e. package. The adhesivelayer 5 may be a cured adhesive layer of the two-component solventlessadhesive described herein. FIGS. 1-3 illustrate the laminated structures1, 2 and 3 with two substrates, however, laminated flexible packagingmaterials, as well as other laminated structures made with thesolventless two-component laminating adhesive described herein,comprising more than two substrates, are within the scope of theinvention, such as 3, 4, 5, 6, 7 and 8, or more, substrates.

Examples of suitable materials for the at least one second substrate 4and first substrate 6 independently include, but are not limited to:paper, aluminum foil, metallized films, coated films, printed films,co-extruded films, polyester films, polyolefin based films, whitepolyolefin based films, polyamide based films, copolymer films, andfilms containing various polymer blends. Typically, the two-partsolventless laminating adhesive is used in flexible laminating packagingwherein one of the substrates is a reverse printed film, such as areverse printed film comprising water-base inks, and the other substrateis a metallized film. In embodiments, the laminated construction, forexample flexible laminated packaging comprises reverse printed film(such as PET) laminated with metallized film (such as metallized PETfilm) or the combination of reverse printed PET film, such as thoseprinted with water-base inks, laminated to one or more secondary filmsof any of the types described herein. Also, one or more of the films maycomprise linear low density polyethylene.

FIG. 2 shows an example of a laminated flexible packaging material 2comprising reverse printed film. The structure shown in FIG. 2 comprisesa substrate 6, such as a clear layer, which has been reverse printed 7on the inside surface thereof, for example a reverse printed PET film,and then bonded to a second substrate 4, for example a metallized filmlayer or other secondary film, using the solventless two-part adhesivecomposition 5. In this type package, the printed material would bereadable on the inside surface of the package.

FIG. 3 shows a further example of a laminated flexible packagingmaterial 3 comprising reverse printed film. The structure shown in FIG.3 comprises a substrate 4, such as a clear layer, which has been reverseprinted 7 on inside surface thereof, for example a reverse printed PETfilm, and then bonded to a substrate 6, for example a metallized filmlayer or other film like linear low density polyethylene using thesolventless two-part adhesive composition 5. In this type of package,the printed material would be readable on the outside of the package.

In an embodiment, such as when using low surface energy substrates, suchas polyolefins, the surface of the substrate to be bonded may besurface-treated to enhance adhesion. Surface treating is well known andany conventional surface treating method can be used as desired for theparticular application. Examples of suitable surface treating methodsinclude corona treatments, chemical treatments, plasma treatments andflame treatments.

The two-component solventless adhesive comprising the relatively highmolecular weight oligomers reduces or eliminates metal decal or inkdecal when using the two-component solventless laminating adhesives onsubstrates or inks that traditionally exhibit decal when conventionaltwo-component solventless adhesives are applied. Examples includelaminations of reverse printed PET film/solventless adhesive/metallizedPET film and reverse water-base ink printed PET/solventlessadhesives/sealant film (i.e., linear low density polyethylene). Forexample, replacing conventional polyols of relative low molecularweights in a two-part solventless adhesive formulation with polyolshaving a molecular weight of about 8,000 g/mole provided significantimprovement causing the failure mode to go from low bonds with 100%metal decal to bonds greater than 400 gli with adhesive failure onreverse printed PET adhesively bonded to metallized PET.

EXAMPLES Comparative Example A

A reverse printed PET film was bonded with a standard solventlesslaminating adhesive (PURELAM® 6000 (prepolymer)/6050 (curative),available from Ashland Inc.) to the metal side of metallized PET film.The bond strength of the laminated structures was tested using ASTMstandard D1876-08 which is incorporated herein by reference in itsentirety and the results are shown graphically in FIG. 4. Initial bonddevelopment is normal, but as the adhesive fully cures the failuremechanism changes from cohesive adhesive failure to demetalization withlow bond strengths.

Comparative Example B

Reverse printed PET with standard water-base acrylic inks were bonded tosecond substrates with three conventional laminating adhesives as notedin FIG. 5. The adhesive applied to make the laminations for thiscomparative example are PURELAM 6000 (prepolymer)/6050 (curative),PURELAM 8810 (prepolymer)/8253 (curative) and FASTCURE™ 110(prepolymer)/230 (curative); all available from Ashland Inc. Thesubstrates for each of the printed film laminates of FIG. 5 are thefollowing:

-   -   A—PET reverse printed with water-base acrylic ink laminated to        PET    -   B—PET reverse printed with water-base acrylic ink laminated to        polyethylene    -   C—biaxially oriented polypropylene (“BOPP”) with water-base        acrylic ink laminated to BOPP    -   D—BOPP with water-base acrylic ink laminated to polyethylene    -   E—BOPP with hybrid ink laminated to BOPP.        The bond strength (gil) was tested for each lamination using        ASTM standard D1876-08. The results are set forth in the graph        in FIG. 5. The bond strength was measured at 14 days of curing        time.

Example 1

A prepolymer (Experimental Prepolymer 1) was made in accordance with theinvention by combining the ingredients set forth in Table 1. Aprepolymer was made for comparative purposes as a control (ControlPrepolymer A) by combining the ingredients set forth in Table 2including polypropylene oxide having a molecular weight of 1,000 g/mole.

TABLE 1 Experimental Prepolymer 1 Materials Wt % Polypropylene oxidemolecular weight 40 8,000 g/mole Polypropylene oxide molecular weight 213,000 g/mole MONDUR MDI 39

TABLE 2 Control Prepolymer A Materials Wt % Polypropylene oxidemolecular weight 40 1,000 g/mole MONDUR MDI 60

Both the Experimental Prepolymer 1 and Control Prepolymer A were mixedwith a PURELAM 6050 isocyanate reactive curative from Ashland Inc.PURELAM 6050 has a hydroxyl number of 270 and viscosity 2,000 cps. Themix ratios for both adhesive formulations were calculated in order toprovide about 20% excess isocyanate (Isocyanate Index=1.2) for eachadhesive. The experimental has good phase stability and comparableviscosity to the control. The adhesive formulation comprisingExperimental Prepolymer 1 and the adhesive formulation comprisingControl Prepolymer A were each applied in making a reverse printed PETfilm to metallized PET film layer structure. Both structures were testedfor adhesion in accordance with standard testing protocols and theresults are set forth in Table 3.

TABLE 3 Adhesion Results Reverse Printed PET film/solventlessadhesive/metallized PET film layer 1 Day 3 Days 7 Days 14 Days ControlPrepolymer/ 1.035 c 0.675 50% MT 0.279 100% MT 0.245 100% MT PURELAM6050 1.010 c 0.681 50% MT 0.212 100% MT 0.216 100% MT 1.096 c 0.607 50%MT 0.342 100% MT 0.251 100% MT Avg. (lbs/in) 1.047 0.654 0.278 0.237Avg. (g/in) 475 297 126 108 EXP #1/PURELAM 0.000 0.186 c 0.929 c 1.351fs 6050 0.000 0.221 c 1.023 c 1.116 a 0.000 0.205 c 0.887 c 1.187 a Avg.(lbs/in) 0.000 0.204 0.946 1.218 Avg. (g/in) 0 93 429 552 c—cohesivefailure a—adhesive failure MT—metal transfer fs—film split/failure

The data set forth in Table 3 demonstrates that the structure made withthe adhesive comprising Experimental Prepolymer 1 provided betteradhesion to the structure compared to the adhesive formulationcomprising Control Prepolymer A.

Examples 2-6

Prepolymers were prepared for Examples 2-6 from the components set forthin Table 4. Examples 2 and 3 are control prepolymers not made with highmolecular weight oligomers and Examples 4, 5 and 6 are made witholigomers having molecular weight of at least 3,000 g/mole. Theprepolymers for Examples 2-6 were prepared by reacting the isocyanate(MONDUR MA 2300 from Bayer Material Science) with the oligomers.

TABLE 4 Example 2 Example 3 Example 4 Example 5 Example 6 Adh Adh AdhAdh Adh Prepolymer mass wt % mass wt % mass wt % mass wt % mass wt %MONDUR MA 2300 78.0 46.8 70.0 44.1 60.0 40.0 47.7 34.4 44.7 32.2Polypropylene 11.0 6.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 glycol molecularweight 1,000 Polypropylene 11.0 6.6 30.0 18.9 0.0 0.0 16.2 11.7 0.0 0.0glycol molecular weight 2,000 Polypropylene 0.0 0.0 0.0 0.0 40.0 26.717.0 12.3 17.0 12.3 glycol molecular weight 3,000 Polypropylene 0.0 0.00.0 0.0 0.0 0.0 19.2 13.9 38.4 27.7 glycol molecular weight 8,000 Total100.0 60.0 100.0 63.0 100.0 66.7 100.0 72.2 100.0 72.2 Curative massmass mass mass mass PURELAM 6050 100 40.0 100 37.0 100 33.3 100 27.8 10027.8 polyester Adhesive Total 100 100 100 100 100 % NCO 16.6 14.8 12.79.6 9.4 Prepolymer OH# Curative 270 270 270 270 270 Mix Ratio 1.7:11.7:1 2:1 2.6:1 2.6:1 Isocyanate Index 1.23 1.25 1.26 1.24 1.21

The prepolymers of Examples 2-6 were used with curative as a laminatingadhesive. The prepolymers were mixed with PURELAM 6050 isocyanatereactive curative from Ashland Inc. Additionally, commercially availablelaminating adhesives from Ashland (PURELAM 6000 (prepolymer)/6050(curative)) and PURELAM 8810 (prepolymer)/8253 (prepolymer)) were run ascontrols. PURELAM 6050 has a hydroxyl number of 270 and viscosity 2,000cps. The mix ratios for all adhesive formulations were calculated inorder to cps. The mix ratios for all adhesive formulations werecalculated in order to provide about 25% excess isocyanate (IsocyanateIndex=1.25) for each adhesive. All of the mixed adhesives had good phasestability.

The adhesives of Examples 2-6 and the two Ashland adhesive controls wereused to make laminated structures with water-base acrylic ink printedsubstrates and metallic substrates and tested for bond strength usingASTM standard D1876-08. The results are set forth in FIGS. 6 and 7. Thecombination of substrates used in the laminated structures are asfollows:

FIG. 6

-   -   PET printed with water-base acrylic ink and PET    -   PET printed with water-base acrylic ink and polyethylene    -   PET printed with water-base acrylic ink and metallic PET film    -   BOPP with water-base acrylic ink and BOPP    -   BOPP with water-base acrylic ink and polyethylene    -   BOPP water-base acrylic ink and metallic BOPP film

FIG. 7

-   -   Reverse Printed PET and metallic PET film    -   PET and metallic PET film    -   PET and metallic polylactic acid

The water-base ink used for the printed substrates in Examples 2-6 andthe Ashland controls was water-base acrylic, formula is MWF-4135 blendedwith 10% MWF-120 Extender, from Wikoff Color Corp., Fort Mill, S.C.,U.S.A. The water-base ink was printed with 550 LPI 4.3 BCM ceramicanilox. Print receptive films were corona treated with 1.9 kiloWatts.Line speed for printing was 210 feet per minute on a Nilpeter FA-4, 16inch web width.

A pilot lab scale solventless adhesive press was used for making thefilm-to-film laminations with the adhesives of Examples 2-6 and theAshland controls with the substrates discussed above and shown in thegraphs of FIGS. 6 and 7. Primary unwind film with 12″ width is coronatreated followed by roll coat with 1-2 lb/ream of the adhesives ofExamples 2-6 and the Ashland controls followed by nipping to secondarycorona treated film that is 12″ wide. Line speed is 40 feet per minute.For laminations including water-base printed film, this film is theprimary web with the solventless adhesive coated directly on top of theink followed by nipping to secondary web. For laminations includingmetallized films, this substrate is the secondary web. The metal side isfacing the solventless adhesive. The laminated film structures are curedat ambient temperature and the bond strengths were measured at 14 daysafter lamination.

What is claimed is:
 1. A two-component solventless adhesive comprising aprepolymer having a) a first oligomer with a molecular weight of atleast about 3,500 g/mole; and b) an isocyanate.
 2. The adhesive of claim1 wherein the oligomer is a polyol selected from the group consisting ofpolyoxypropylene glycol, polyoxyethylene glycol, copolymers of ethyleneoxide and propylene oxide and polyester polyols.
 3. The adhesive ofclaim 1 wherein the first oligomer is in an amount of at least about 20%by weight of the prepolymer.
 4. The adhesive of claim 1 wherein theisocyanate is selected from the group consisting of hexamethylenediisocyanate, toluene diisocyanate, diphenylmethane diisocyanate,allophonate modified diphenylmethane diisocyanate, m-phenylenediisocyanate, p-phenylene diisocyanate, bitolylene diisocyanate,cyclohexane diisocyanate, bis-(isocyanatomethyl)cyclohexane,dicyclohexylmethane diisocyanate, dimer acid diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate and its methyl ester,isophorone diisocyanate, methyl cyclohexane diisocyanate, 1,5-napthalenediisocyanate, xylylene diisocyanate and methyl derivatives thereof,xylene diisocyanate and methyl derivatives thereof, polymethylenepolyphenyl isocyanates, chlorophenylene-2,4-diisocyanate, polyphenylenediisocyanates, isophorone diisocyanate, hydrogenated methylene diphenylisocyanate, tetramethyl xylene diisocyanate, hexamethylene diisocyanate,trimer of isophorone diisocyanate, trimer of hexamethylene diisocyanate,biuret of hexamethylene diisocyanate and combinations thereof.
 5. Theadhesive of claim 1 comprising a curative having an isocyanate reactivecomponent selected from the group consisting of polyhydroxyls,polythiols, polyamines and combinations thereof.
 6. A two-componentsolventless adhesive comprising a prepolymer having a) a first oligomerwith a molecular weight of about 2,000 g/mole to about 5,000 g/mole asecond oligomer having a molecular weight of about 5,500 g/mole to about10,000 g/mole; and b) an isocyanate.
 7. A process for making a laminatedstructure comprising the steps of a) providing a first substrate and asecond substrate each having an upper surface and a lower surfacewherein at least one of the first substrate or second substrate isselected from the group consisting of substrate having water-base ink, asubstrate having a metallized film and combinations thereof; b)providing the adhesive of claim 1 and applying the adhesive to at leastone surface of at least one of the first substrate or second substrate;and c) bonding the first substrate to the second substrate to form alaminated structure.
 8. The process of claim 7 wherein the adhesive isapplied by a method selected from the group consisting of roll coating,gravure, and offset gravure.
 9. The process of claim 7 wherein the firstsubstrate is a reverse printed film comprising a water-base adhesive andthe second substrate comprises a metallized film.
 10. The process ofclaim 7 wherein the first substrate comprises a metallized film and thesecond substrate is a reverse printed film comprising a water-base ink.11. The process of claim 7 wherein at least one of the first substrateor second substrate is surface treated.